Light emitting device using phosphor powder

ABSTRACT

The present invention is a light emitting device which uses a specific phosphor powder. The phosphor powder is a combination of cerium (Ce) and lithium aluminum oxide (LiAlO 2 ). They are mixed under a specific range of composition ratio. With the specific phosphor powder applied, the light emitting device has advantages in a low cost, a reduced power consumption, an easy production, a long life, and so on. In addition, a transformation efficiency of the phosphor powder is high and so a light emitting efficiency of the light emitting device is enhanced.

FIELD OF THE INVENTION

The present invention relates to a light emitting device; moreparticularly, relates to a phosphor powder combination having a rareearth element of cerium for effectively improving a light emittingefficiency.

DESCRIPTION OF THE RELATED ARTS

White light emitting diode (LED) and high brightness LED are two majorfields in developing LEDs. Under a request of environmental protectionand a trend in high price powers, a white-light LED becomes an urgentneed in the fields of displaying and lightening for its power saving andlightweight.

Materials used in producing white-light LEDs are divided into organicLEDs and non-organic LEDs. Two major white-light LEDs in the market areas follows:

(a) One is in the main stream of the LEDs, which has a blue LED excitinga phosphor powder of yttrium aluminum garnet (YAG). As shown in FIG. 3,a blue LED chip 21 emits a wavelength between 400 nanometers (nm) and530 nm; and an optical adhesive 22 mixed with a phosphor powder of YAGcovers around the blue LED chip 21. The light emitted from the blue LEDchip 21 excites the YAG phosphor powder for obtaining a yellow lighthaving a 555 nm wavelength, where the yellow light is mixed in a lenswith some extra complementary blue light emitted from the blue LED chip21 to obtain a white light.

However, the prior art obtaining the white light by mixing the bluelight emitted from the blue LED and the yellow light emitted from theYAG phosphor powder has the following disadvantages:

-   -   (1) Because the blue light plays the major role in the whole        process, color temperature is high and uneven.    -   (2) Because the wavelength of the blue light emitted is changing        with the temperature, color of the white light obtained is not        easily controlled.    -   (3) And, color rendition is bad for red light is weak.

(b) Another prior art is a white-light LED having red-blue-greenphosphor powders with a high light emitting efficiency and a high colorrendition. Yet, the materials for different color phosphor powders hasdifferent voltages, so that control design becomes complex and lightmixture becomes difficult. As shown in FIG. 4, an ultraviolet (UV) LEDgrain 31 excites an optical adhesive 32 evenly mixed with a certainratio of red-blue-green phosphor powders to obtain a white light ofthree mixed wavelengths. The white light of three mixed wavelengths hasa high rendition; but has a bad light emitting efficiency. In addition,because the UV LED grain 31 is used as a light source and may do harm tohuman body, the UV LED grain 31 is blocked inside the whole white lightLED.

According to the prior arts, their disadvantages include insufficientbrightness and uneven luminescence, where light transformationefficiencies has to be enhanced, luminescence evenness has to beimproved and the UV leakage has to be prevented, if used. Hence, theprior arts do not fulfill all users' requests on actual use.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to obtain a light emittingdevice with a low cost, a reduced power consumption, an easy production,a uniformed light color, a non-bias color and a long lifetime, while,after adding a rare earth element to a phosphor powder combination, alight transformation efficiency of the phosphor powder combination isenhanced for improving a light emitting efficiency.

To achieve the above purpose, the present invention is a light emittingdevice using a phosphor powder, comprising a light emitting element anda phosphor powder layer, where, through mixing colors of micro-lightsemitted from crystal grains of a phosphor powder combination in thephosphor powder layer, a light spectrum emitted from the light emittingelement is transformed into a requested light spectrum. Accordingly, anovel light emitting device u sing a phosphor powder is obtained.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The present invention will be better understood from the followingdetailed descriptions of the preferred embodiments according to thepresent invention, taken in con junction with the accompanying drawings,in which

FIG. 1 is the structural view showing the first preferred embodimentaccording to the present invention;

FIG. 2 is the structural view showing the second preferred embodiment;

FIG. 3 is the view of the general white-light LED; and

FIG. 4 is the view of the white-light LED excited by the UV light.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

The following descriptions of the preferred embodiments are provided tounderstand the features and the structures of the present invention.

Please refer to FIG. 1, which is a structural view showing a firstpreferred embodiment according to the present invention. As shown in thefigure, the present invention is a light emitting device using aphosphor powder, comprising a light emitting element 11 a and a phosphorpowder layer 12 a, where the device has a low cost, a reduced powerconsumption, an easy production, a uniformed and non-biased light colorand a long lifetime; and, after adding a rare earth element, a lighttransformation efficiency of a phosphor powder combination is enhancedfor improving a light emitting efficiency.

The light emitting element 11 a emits a light spectrum, where the lightemitting element 11 a is a light emitting diode (LED), an electronicgun, an organic light emitting diode (OLED) or a general light source.

The phosphor powder layer 12 a is formed on the light emitting element11 a to adjust a light color of the light emitting element 11 a, wherethe phosphor powder layer 12 a has a flat surface, an arc surface or anygeometric surface.

On using the present invention, the phosphor powder layer 12 a is formedon the light emitting element 11 a through a wet coating or a drydeposition. The phosphor powder layer 12 a has a phosphor powdercombination obtained by a mixture under a dose composition ratio, wherea wavelength emitted from the light emitting element 11 a is changed bymixing colors of micro-lights emitted from crystal grains of thephosphor powder combination. The phosphor powder combination is Ce(cerium):LiAlO₂ (lithium aluminum oxide) emitting lights of threeprimary colors of red, blue and green, which has a dose compositionratio of 0.0001 percent (%) to 5% and is mixed in a transparent mediumto form the phosphor powder layer 12 a. The phosphor powder layer 12 aemits requested light spectrum, like an ultra violet, a blue light, awhite light or other light source, through mixing colors of micro-lightsemitted from crystal grains of the phosphor powder combination with alight spectrum provided by the light emitting element 11 a, where thetransparent medium is made of silicon oxide, titanium oxide or an epoxyresin.

During the wet coating, the phosphor powder, which is Ce:LiAlO₂ and hasa dose composition ratio of 0.0001% to 5%, and the transparent mediumare directly weighted to be added in a proper solvent for an evenmixture; or, the phosphor powder and the transparent medium are mixedunder an atomic state in a solution through a sol-gel method or aco-precipitation method to be added in the solvent. Then the mixture iscoated on the light emitting element 11 a through spin-coating orprint-coating for obtaining a light spectrum excited by a light.

During the dry deposition, the phosphor powder, which is Ce:LiAlO₂ andhas a dose composition ratio of 0.0001% to 5%, and the transparentmedium are directly weighted to obtain a target; or, the phosphor powderand the transparent medium are mixed under an atomic state in a solutionthrough a sol-gel method or a co-precipitation method to obtain atarget. Then the target is deposited on the light emitting element 11 athrough evaporation, sputtering or ion-beam deposition for obtaining alight spectrum excited by a light.

Therein, the rare earth element of Ce in the Ce:LiAlO₂ phosphor powdercombination is further any rare earth element, like lanthanum (La),praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium(Sc) or yttrium (Y); and, the LiAlO₂ in the Ce:LiAlO₂ phosphor powdercombination is further lithium gallium oxide (LiGaO₂) lithium siliconoxide (Li₂SiO₃), lithium germanium oxide (LiGeO₃), sodium aluminum oxide(NaAlO₂), sodium germanium oxide (Na₂GeO₃), sodium silicon oxide(Na₂SiO₃), lithium phosphor oxide (Li₃PO₄) lithium arsenic oxide(Li₃AsO₄), lithium vanadium oxide (Li₃VO₄), lithium magnesium germaniumoxide (Li₂MgGeO₄), lithium zinc germanium oxide (Li₂ZnGeO₄), lithiumcadmium germanium oxide (Li₂CdGeO₄), lithium magnesium silicon oxide(Li₂MgSiO₄), lithium zinc silicon oxide (Li₂ZnSiO₄), lithium cadmiumsilicon oxide (Li₂CdSiO₄), sodium magnesium germanium oxide (Na₂MgGeO₄),sodium zinc germanium oxide (Na₂ZnGeO₄) or sodium zinc silicon oxide(Na₂ZnSiO₄). Thus, a novel light emitting device using a phosphor powderis obtained.

Please refer to FIG. 2, which is a structural view showing a secondpreferred embodiment. As shown in the figure, the present invention is alight emitting device using a phosphor powder, comprising a lightemitting element 11 b and a phosphor powder layer 12 b, where the devicehas a low cost, a reduced power consumption, an easy production, auniformed and non-biased light color and a long lifetime; and, afteradding a rare earth element, a light transformation efficiency of aphosphor powder combination is enhanced for improving a light emittingefficiency.

The light emitting element 11 b emits a light spectrum, where the lightemitting element 11 b is a LED, a n electronic gun, an OLED or a generallight source.

The phosphor powder layer 12 b is formed on the light emitting element11 b to adjust a light color of the light emitting element 11 b, wherethe phosphor powder layer 12 b has a packaging layer 13 made of anacrylate resin, a fluoro resin, an epoxy resin, a Si₃N₄ film or a DLCfilm; and the phosphor powder layer 12 b has a flat surface, an arcsurface or any geometric surface.

On using the present invention, the phosphor powder layer 12 b is formedon the light emitting element 11 b through a wet coating or a drydeposition. The phosphor powder layer 12 b has a phosphor powdercombination obtained by a mixture under a dose composition ratio, wherea wavelength emitted from the light emitting element 11 b is changed bymixing colors of micro-lights emitted from crystal grains of thephosphor powder combination. The phosphor powder layer 12 b has aphosphor powder combination of Ce:LiAlO₂ emitting lights of threeprimary colors of red, blue and green, which has a dose compositionratio of 0.0001% to 5% and is mixed in a transparent medium to for thephosphor powder layer 12 b. The phosphor powder layer 12 b emitsrequested light spectrum, like an ultra violet, a blue light, a whitelight or other light source, through mixing colors of micro-lightsemitted from crystal grains of the phosphor powder combination with alight spectrum provided by the light emitting element 11 b, where thetransparent medium is made of silicon oxide, titanium oxide or an epoxyresin.

During the wet coating, the phosphor powder, which is Ce:LiAlO₂ and hasa dose composition ratio of 0.0001% to 5%, and the transparent mediumare directly weighted to be added in a proper solvent; or, the phosphorpowder and the transparent medium are mixed under an atomic state in asolution through a sol-gel method or a co-precipitation method to beadded in the solvent. Then the mixture is coated on the light emittingelement 11 b through spin-coating or print-coating, and the coatedmixture is hot-dried to remove the solvent and water. Then a packaginglayer 13 is coated or deposited on the coated mixture, where thepackaging layer 13 is made of an acrylate resin, a fluoro resin, anepoxy resin, a Si₃N₄ film or a DLC film.

During the dry deposition, the phosphor powder, which is Ce:LiAlO₂ andhas a dose composition ratio of 0.0001% to 5%, and the transparentmedium are directly weighted to obtain a target; or, the phosphor powderand the transparent medium are mixed under an atomic state in a solutionthrough a sol-gel method or a co-precipitation method to obtain atarget. Then the target is deposited on the light emitting element 11 bthrough evaporation, sputtering or ion-beam deposition to form thephosphor powder layer 12 b for obtaining a light spectrum excited by alight. And then a packaging layer 13 is formed as a protection on thephosphor powder layer 12 b through depositing a Si₃N₄ film or a DLC filmor coating an acrylate resin, an epoxy resin or a fluoro resin.

Therein, the rare earth element of Ce in the Ce:LiAlO₂ phosphor powdercombination is further any rare earth element, like La, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc or Y; and, the LiAlO₂ in theCe:LiAlO₂ phosphor powder combination is further LiGaO₂, Li₂SiO₃,LiGeO₃, NaAlO₂, Na₂GeO₃, Na₂SiO₃, Li₃PO₄, Li₃AsO₄, Li₃VO₄, Li₂MgGeO₄,Li₂ZnGeO₄, Li₂CdGeO₄, Li₂MgSiO₄, Li₂ZnSiO₄, Li₂CdSiO₄, Na₂MgGeO₄,Na₂ZnGeO₄ or Na₂ZnSiO₄. Thus, a novel light emitting device using aphosphor powder is obtained.

To sum up, the present invention is a light emitting device using aphosphor powder, where the present invention has a low cost, a reducedpower consumption, an easy production, a uniformed and non-biased lightcolor and a long lifetime; and, after adding a rare earth element, alight transformation efficiency of a phosphor powder combination isenhanced for improving a light emitting efficiency.

The preferred embodiments herein disclosed are not intended tounnecessarily limit the scope of the invention. Therefore, simplemodifications or variations belonging to the equivalent of the scope ofthe claims and the instructions disclosed herein for a patent are allwithin the scope of the present invention.

1. A light emitting device using a phosphor powder, comprising: a lightemitting element, said light emitting element obtaining a lightspectrum; and a phosphor powder layer, said phosphor powder layer havinga phosphor powder combination of Ce (cerium): LiAlO₂ (lithium aluminumoxide), said phosphor powder layer being deposed on said light emittingelement to change light color of said light emitting element.
 2. Thedevice according to claim 1, wherein said light emitting element is alight source selected from a group consisting of a light emitting diode(LED), an electronic gun and an organic light emitting diode (OLED). 3.The device according to claim 1, wherein said phosphor powder layer hasa phosphor powder combination emitting lights of three primary colors ofred, blue and green.
 4. The device according to claim 3, wherein saidphosphor powder combination has a dose composition ratio between 0.0001percent (%) and 5%.
 5. The device according to claim 1, wherein saidcomponent of Ce in said phosphor powder combination of Ce:LiAlO₂ isfurther a component selected from a group consisting of lanthanum (La),praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm),europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium(Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium(Sc) and yttrium (Y).
 6. The device according to claim 1, wherein saidcomponent of LiAlO₂ in said phosphor powder combination of Ce:LiAlO₂ isfurther a component selected from a group consisting of lithium galliumoxide (LiGaO₂), lithium silicon oxide (Li₂SiO₃), lithium germanium oxide(LiGeO₃), sodium aluminum oxide (NaAlO₂), sodium germanium oxide(Na₂GeO₃), sodium silicon oxide (Na₂SiO₃), lithium phosphor oxide(Li₃PO₄), lithium arsenic oxide (Li₃AsO₄), lithium vanadium oxide(Li₃VO₄), lithium magnesium germanium oxide (Li₂MgGeO₄), lithium zincgermanium oxide (Li₂ZnGeO₄), lithium cadmium germanium oxide(Li₂CdGeO₄), lithium magnesium silicon oxide (Li₂MgSiO₄), lithium zincsilicon oxide (Li₂ZnSiO₄), lithium cadmium silicon oxide (Li₂CdSiO₄),sodium magnesium germanium oxide (Na₂MgGeO₄), sodium zinc germaniumoxide (Na₂ZnGeO₄) and sodium zinc silicon oxide (Na₂ZnSiO₄).
 7. Thedevice according to claim 1, wherein said phosphor powder layer changesa wavelength of said light emitting element through mixing colors ofmicro-lights emitted from said phosphor powder combination.
 8. Thedevice according to claim 1, wherein said phosphor powder layer has atransparent medium mixed with said phosphor powder combination.
 9. Thedevice according to claim 8, wherein said transparent medium is made ofa material selected from a group consisting of silicon oxide, titaniumoxide and an epoxy resin.
 10. The device according to claim 1, whereinsaid phosphor powder layer is coated on said light emitting elementthrough a wet coating.
 11. The device according to claim 1, wherein saidphosphor powder layer is coated on said light emitting element through adry deposition.
 12. The device according to claim 1, wherein said deviceemits a light selected from a group consisting of an ultraviolet light,a blue light and a white light.
 13. The device according to claim 1,wherein said phosphor powder layer has a geometric surface selected froma group consisting of a flat surface and an arc surface.
 14. The deviceaccording to claim 1, wherein said phosphor powder layer furthercomprises a packaging layer.
 15. The device according to claim 14,wherein said packaging layer is made of a material selected from a groupconsisting of an acrylate resin, a fluoro resin, an epoxy resin, asilicon nitride (Si₃N₄) film and a diamond-like carbon (DLC) film.